I have just starting to use calibre Version 0.7.40 and think it is a wonderful application.
I just downloaded the updated version 0.7.42 but every time I try to install this it gets near the end of the install and fails with the message "unable to create cache. Contact your support ". I then cancel the installation and it then rolls the process back.

Hi Phil, Looks like you have people stumped (myself included). What Operating System are you using? What are the specs of your machine? Have you tried uninstalling the previous version before attempting the re-install? Calibre is not running when you try the install?

An error -2147286775, means that [a docfile is "corrupt"] (a docfile is an OLE Structured Storage File, for storing objects in a file format).

My PC OS is xp pro up to date with all the updates.
I have just uninstalled the 0.7.40 version and tried to install the 0.7.42 version.I got the same error.
I then reinstalled the 0.7.40 version and that installed OK with no problems.